The present invention relates generally to wheel mountings and more particularly relates to means for positioning the anti-friction bearings which support a hub for rotation about a shaft.
Wheel hubs are commonly supported for rotation on a pair of spaced apart bearings which are subjected to radial and side loading forces during operation. Existing anti-friction ball bearings are well designed to withstand the radial loading forces. The side loading forces encountered by the wheel hubs and inner race rings of these bearings are typically resisted by confining the inner races with a shoulder on either the shaft or spindle and a spacer sleeve positioned between the adjacent surfaces of the inner races. The bearing outer race rings are typically restrained against side loading forces by hub shoulders which abut the outer rings at their adjacent edges or by restraining one bearing outer race ring against axial movement in either direction. This latter type of restraint usually includes a hub shoulder restraining one edge of the outer race ring and a washer or pressure ring coupled with the hub for restaining the other edge of that race ring.
Additional manufacturing, casting and boring expenses are required when such hub shoulders must be provided within a wheel hub. Further, assembly of the hub onto the spindle is less efficient where the hub has shoulders for positioning the bearings. Therefore it would be desirable to restrain the outer race rings without the use of such shoulders.
Positioning either one or both outer race rings adjacent a hub shouler can cause reliability problems and increase assembly time and expense. Reliability of a hub bearing support would be reduced if the outer races and hub are not restrained or coupled so as to resist side loading forces. If, during assembly, a bearing outer race were positioned against a hub shoulder, and a sleeve spacer then mounted onto the spindle to separate the other bearing a defined distance from the first bearing, the second bearing outer race would not abut its respective hub shoulder if the sleeve were unknowingly long. Thus the assembler would not be aware that the second bearing outer race did not have axial restaint as expected and that the hub would be able to shift axially with respect to that bearing race. Therefore, slippage of the hub on the bearing may occur under side loading circumstances since the bearing outer race and hub were not coupled.
When a spacer sleeve is short, assembly time and cost may be increased because the bearing outer races will abut their respective hub shoulders but the inner races will not abut the spacer sleeve. Accordingly the bearing inner races would not be restrained although the outer races would be restrained by the hub shoulder. The assembler would not be aware that the inner race ring was not restrained by the sleeve. Thus, as the spindle nut was tightened to axially restrain the inner races, the second bearing inner race could be displaced axially from its outer race and if too great a pressure were exerted while tightening the nut, premature failure of the bearings could occur.
When only one outer race ring is restrained to counter side loading, only one hub shoulder is required and the other side of the outer race ring is restrained by a washer, collar or similar pressure ring. With this type of structure, the side loading forces are absorbed by one bearing outer race ring while the other bearing outer race ring encounters no side loading forces. If each bearing outer race absorbed some of the side loading forces, the expected life of that bearing would probably be greater then that of the bearing race which must resist all the side loading forces.
Some wheel mounting structures include tapered bearings upon which the hub rotates about the shaft. Since the tapered bearing tract within the inner race must be properly contoured so that the bearing will freely roll, excess tightening of the nut to restain the inner race rings can distort the tract. Thus the pressure used to confine this type of bearing is crucial and the bearing must be rechecked often to assure that it functions properly and that the nut has not worked loose.